Implement N4387, "Improving pair and tuple", and LWG 2367.

Implement N4387, "Improving pair and tuple", and LWG 2367.

2015-06-30  Ville Voutilainen  <ville.voutilainen@gmail.com>

	Implement N4387, "Improving pair and tuple", and LWG 2367.

	* include/bits/stl_pair.h (_ConstructiblePair,
	_ImplicitlyConvertiblePair, _MoveConstructiblePair,
	_ImplicitlyMoveConvertiblePair): New.
	(pair()): Constrain it.
	(pair(const _T1&, const _T2&), pair(const pair<_U1, _U2>&),
	pair(_U1&&, const _T2&), pair(const _T1&, _U2&&), pair(_U1&&, _U2&&),
	pair(pair<_U1, _U2>&&)): Make conditionally explicit.
	* include/std/tuple (_TC, tuple::_TC2, tuple::TCC, tuple::TMC): New.
	(tuple()): Constrain it.
	(tuple(const _UElements&...), tuple(_UElements&&...),
	tuple(const tuple<_UElements...>&), tuple(tuple<_UElements...>&&),
	tuple(allocator_arg_t, const _Alloc&, const _UElements&...),
	tuple(allocator_arg_t, const _Alloc&, _UElements&&...),
	tuple(allocator_arg_t, const _Alloc&, const tuple<_UElements...>&),
	tuple(allocator_arg_t, const _Alloc&, tuple<_UElements...>&&),
	tuple(const pair<_U1, _U2>&), tuple(pair<_U1, _U2>&&),
	tuple(allocator_arg_t, const _Alloc&, const pair<_U1, _U2>&),
	tuple(allocator_arg_t, const _Alloc&, pair<_U1, _U2>&&)): Make
	conditionally explicit.
	* include/experimental/functional (__boyer_moore_array_base): Name
	array type explicitly instead of using an empty braced-init-list.
	* testsuite/20_util/pair/cons/explicit_construct.cc: New.
	* testsuite/20_util/pair/piecewise.cc: Use piecewise_construct.
	* testsuite/20_util/pair/requirements/dr2367.cc: New.
	* testsuite/20_util/tuple/cons/explicit_construct.cc: New.
	* testsuite/20_util/tuple/requirements/dr2367.cc: New.

From-SVN: r225189